The present disclosure is broadly concerned with microbial fuel cells. More particularly, it is concerned with a high power density yeast-catalyzed microbial fuel cell having a biofilm of baker's yeast cells adhered to the anode.
There is great interest is using microbial fuels cells (MFCs) to harvest energy from diverse natural feeds such as wastewater and ocean sediments. The high efficiency of conversion of biomass energy directly to electrical energy in such MFCs makes this a compelling approach to both large and small scale power generation. Dirty, untreated natural sugars could be used as fuel in MFCs catalyzed by inexpensive and self-renewing microbes. Abundant, widely available natural sugars such as raw tree sap could be used to provide an emergency power supply for sensors and other devices having low power requirements. However, thus far the amount of power generated by such MFCs per unit of volume is very low. In order to effectively use readily available natural feed sources such as plants as an interface for fuel cell power generation, the power density of such fuel cells must be increased substantially.
Yeasts are particularly well-suited for use in MFCs because they are harmless, widely available and robust under a broad range of conditions. Baker's yeast (S. Cerevisiae) is commonly used in the biofuels industry to convert six carbon sugars to alcohol through fermentation. Baker's yeast may be employed as an inexpensive and self-renewing MFC catalyst when used in combination with an electron mediator. However, attempts to use free floating or planktonic yeast cells in a solution in MFCs have necessarily involved a fairly low concentration of cells, yielding very low fuel cell power density. Formation of a biofilm on the fuel cell electrode would increase the number of yeast cells able to participate in power generation. And attempts to use biofilms having a higher concentration of cells to boost fuel cell power densities have been successful with other types of cells, such as Geobacter. However, in order to coax baker's yeast to form biofilms, it has generally been necessary to employ specialized experimental conditions and techniques such as nutrient starvation, or targeted genetic mutation.
Accordingly, there is a need for a high power density microbial fuel cell that can use baker's yeast as a catalyst. There is also a need for a method for preparation of a yeast biofilm that will significantly increase cell density adjacent an electrode, resulting in a higher power density microbial fuel cell. Such a method should be relatively uncomplicated and capable of practice in the field, under emergency conditions. There is also a need for a method for preparation of multiple yeast biofilms on the same anode to further increase the power density of the microbial fuel cell.